Mouse Test Lab

Mouse Test Lab is a free set of in-browser tools for checking how a mouse actually behaves—no install required.

You can test button mapping (left, right, middle, and extra buttons), scroll-wheel direction and smoothness, double-click timing, clicks per second (CPS), and DPI-related tracking.

It's useful if you just bought a new mouse, you're troubleshooting a flaky one, or you want a quick way to measure click and scroll behavior in the browser.